// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_MISC_KERNEL_H
#define EIGEN_MISC_KERNEL_H

namespace Eigen {

namespace internal {

/** \class kernel_retval_base
 *
 */
template<typename DecompositionType>
struct traits<kernel_retval_base<DecompositionType>>
{
	typedef typename DecompositionType::MatrixType MatrixType;
	typedef Matrix<typename MatrixType::Scalar,
				   MatrixType::ColsAtCompileTime, // the number of rows in the "kernel matrix"
												  // is the number of cols of the original matrix
												  // so that the product "matrix * kernel = zero" makes sense
				   Dynamic,						  // we don't know at compile-time the dimension of the kernel
				   MatrixType::Options,
				   MatrixType::MaxColsAtCompileTime, // see explanation for 2nd template parameter
				   MatrixType::MaxColsAtCompileTime	 // the kernel is a subspace of the domain space,
													 // whose dimension is the number of columns of the original matrix
				   >
		ReturnType;
};

template<typename _DecompositionType>
struct kernel_retval_base : public ReturnByValue<kernel_retval_base<_DecompositionType>>
{
	typedef _DecompositionType DecompositionType;
	typedef ReturnByValue<kernel_retval_base> Base;

	explicit kernel_retval_base(const DecompositionType& dec)
		: m_dec(dec)
		, m_rank(dec.rank())
		, m_cols(m_rank == dec.cols() ? 1 : dec.cols() - m_rank)
	{
	}

	inline Index rows() const { return m_dec.cols(); }
	inline Index cols() const { return m_cols; }
	inline Index rank() const { return m_rank; }
	inline const DecompositionType& dec() const { return m_dec; }

	template<typename Dest>
	inline void evalTo(Dest& dst) const
	{
		static_cast<const kernel_retval<DecompositionType>*>(this)->evalTo(dst);
	}

  protected:
	const DecompositionType& m_dec;
	Index m_rank, m_cols;
};

} // end namespace internal

#define EIGEN_MAKE_KERNEL_HELPERS(DecompositionType)                                                                   \
	typedef typename DecompositionType::MatrixType MatrixType;                                                         \
	typedef typename MatrixType::Scalar Scalar;                                                                        \
	typedef typename MatrixType::RealScalar RealScalar;                                                                \
	typedef Eigen::internal::kernel_retval_base<DecompositionType> Base;                                               \
	using Base::dec;                                                                                                   \
	using Base::rank;                                                                                                  \
	using Base::rows;                                                                                                  \
	using Base::cols;                                                                                                  \
	kernel_retval(const DecompositionType& dec)                                                                        \
		: Base(dec)                                                                                                    \
	{                                                                                                                  \
	}

} // end namespace Eigen

#endif // EIGEN_MISC_KERNEL_H
